hallways后面为什么要加s

hallway，意思是过道、走廊，是可数名词，所以要加s，例如：

1.I put up my posters in hallways and in the classroom.我把海报张贴在走廊和教室里。

2.He stood in the narrow hallway just outside the door.他就站在门外狭窄的走廊里。

3.There were low, muffled voices rising from the hallway.从走廊里隐约传来了低沉的说话声。